My first 12v/ Voltage problems

SingycabLongbox · Dec 20, 2021

Hello yall
Just bought my first diesel, a 1990(?) W 2(3?)50 with an nv4500 in it. Got a lot of k- 560,000kms. I got it for a good price, especially where I live, I've owned it less than 24 hrs and I've had 2 offers on it from driving it around.

I digress

I put the question marks above because the truck seems to be frankensteined together... It's VIN says its a 90 however its got a 92 grill and the truck is intercooled which indicates at least 91.5 however it may have been added after- I really don't know. It seems the owner previous to the one I bought it off of built the truck up. The guy I bought it off of didn't know much I don't think.

I am quite familiar with gassers but this is my first diesel and I am excited to learn and work on this truck. I'm heading to college for HD diesels next fall. I'm not entirely uneducated but I know I have a LOT to learn

First impressions, it runs and drives damnn good for its Kms, it had been sitting for a month and started first crank, shifted smooth no issues there. Brakes took some time to feel right but the 3 hour drive home fixed that.

The biggest issue is it has some kind of voltage issue, the trucks voltemeter slowly goes down while driving until theres not enough power to run the lights. Obvious first thought is alternator but buddy had installed some kind of voltage regulator, said it worked and then stopped after a couple weeks I believe. Any thoughts on why this is? Hoping the fix makes all the electronics work 🤞

Needs cab corners, rockers, front cab mounts and driver floor. Fenders are good all the way around. Thing hauls ass and ROLLS COAL OH MY GOD. Im turning the pump down because its just too much and it tanks my fuel economy.
This truck will be my daily commuter to college and I need it to get maximum mpg. Will definitely be asking questions on how to achieve that.

TIA for all the help

Also please move to another sub forum if this is the wrong one, it kinda does have to do with making the truck move as I can't legally drive it without lights...

daword2011 · Dec 20, 2021

On the title, is it a 90? If so someone modded on 91.5+ front clip. Not an uncommon mod. And intercooling the trucks really isn't too much of an ordeal.

However, for charging, does the truck have a PCM in the driver fender well? Or does it have the voltage regulator on the firewall? Track the alternator wire to find out. Wondering if they swapped in a whole intercooled engine or modded the OEM engine.

Firewall regulator, change it out and see how it reacts. If it's a PCM them mod it to accept an internal or external regulator. The pcms are notorious for randomly messing up charging.

Sent from my Pixel 4a using Tapatalk

SingycabLongbox · Dec 20, 2021

daword2011 said:
On the title, is it a 90? If so someone modded on 91.5+ front clip. Not an uncommon mod. And intercooling the trucks really isn't too much of an ordeal.

However, for charging, does the truck have a PCM in the driver fender well? Or does it have the voltage regulator on the firewall? Track the alternator wire to find out. Wondering if they swapped in a whole intercooled engine or modded the OEM engine.

Firewall regulator, change it out and see how it reacts. If it's a PCM them mod it to accept an internal or external regulator. The pcms are notorious for randomly messing up charging.

Sent from my Pixel 4a using Tapatalk

Title says its a 90 w250 but it has the 350 badges and I think springs, and the aforementioned stuff too, like I said its frankensteined which freaks me out a bit because i dont know how it was built.

as for the pcm ill have to check this week, i think its the voltage regulator because PO installed it on the fender an aftermarket one

tobylou8 · Dec 20, 2021

If it's draining, the battery isn't accepting the charge or being charged. Why? Cheap reman alternator, cheap chinese voltage regulator, and classicly faulty Chrysler wiring all working together to not do one simple thing. Or the battery is bad. Finally took mine to the shop where they have better diagnostic tools. If all the things mentioned have been done to your 90, who knows what's been done to the electronics as there are many shade tree remedies and most work in and of themselves. IF you have an amalgamation of "fixes"... you need good tools and electronics knowledge. I replaced everything related to the charging problem I had, fixed it and now the lights pulse all the time. If your voltage regulator is external, then the PCM has been bypassed or it has an ECM and that shouldn't be hooked into the charging system.

9297oldram · Dec 20, 2021

It's normal for the volts to drop when a cold start is done, it's the gridheaters cycling. The gridheaters cycle to help it start better when it's cold and to reduce the smoke until the engine gets close to 60 degrees.

SingycabLongbox · Dec 21, 2021

It stays dropped and only gets lower until even my headlights dont work

9297oldram · Dec 21, 2021

The external regulators case has to be grounded good for it to work. It's a little more then a new Alternator but you can buy a 1 wire alternator and have no more problems. I'm using one on my 92's engine in my Ford , you can get them at PAPERFORMANCE.

tobylou8 · Dec 21, 2021

9297oldram said:
The external regulators case has to be grounded good for it to work. It's a little more then a new Alternator but you can buy a 1 wire alternator and have no more problems. I'm using one on my 92's engine in my Ford , you can get them at PAPERFORMANCE.

THIS!!!!

My first 12v/ Voltage problems

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